Problem with camera orientation in motion tracking
The problem with your shot is that there is no parallax information. The camera is just panning, but there is no displacement. In other words the camera is just rotating but stationary in the same place. The normal camera solver cannot reconstruct the distance to the tracked points to do a proper 3d solution on this kind of shots.



You need to solve as tripod.



Note that when you do that there is no way to get a proper reconstruction of the space in 3D. The tracking points are then projected in a spherical way around the camera.



Tripod solve will not give you real 3D information.

From the wiki: 


  tripod can be used for footage where the camera does not move and only
  rotates. Such footage can't be tracked with a generic solver approach,
  and it's impossible to determine the actual feature points in space
  due to a lack of information. So this solver will solve only the
  relative camera rotation and then reproject the feature points into a
  sphere, with the same distance between feature and camera for all
  feature points.


To integrate 3D elements into the shot you're going to need to know the actual lens/sensor used and try to calculate the camera height manually.